IDENTIFICATION OF A RAT TESTIS-SPECIFIC GENE ENCODING A POTENTIAL RATOUTER DENSE FIBER PROTEIN

Screening of a vat testis expression library with an antiserum specifi c for an outer dense fibre (ODF) has led to the identification of a ge ne encoding for a putative protein previously unknown as a component o f the sperm tail. This gene has been designated tpx-1 by virtue of its homology with the mouse and human gene of the same name (79 and 73%, respectively). The tpx-1-like gene encoded a 1.6-kb mRNA and a 243-ami no-acid protein that had significant homology with members of the cyst eine-rich secretory protein (CRISP) family and partial homology with s everal venom/allergen proteins from both plants and insects. During ra t spermatogenesis, the tpx-1-like transcript was first detected by in situ hybridization in low levels in late pachytene spermatocytes. Low but detectable levels of expression continued up to step 5 round sperm atids, after which expression levels increased dramatically to a maxim um in step 11-12 spermatids. Progressively decreasing levels of expres sion were detected in up to step 17 elongating spermatids. Testicular somatic cells did not contain detectable tpx-1-like transcript. This p attern of expression is consistent with published data on the developm ent of the ODF in spermatogenesis and, when taken together with a comp arison of the predicted amino acid sequence of tpx-1 with the animo ac id analysis of a 29-kDa rat ODF protein, suggests that the tpx-1-like gene may encode for this protein. (C) 1998 Wiley-iiss, Inc.